Simulating single speed

[Smurfy]

34&14 or 50&21 according to the calculator for 65"

Check out the chain angle for both of those. I'm guessing that neither will be perfect. If you normally use the lowest gear to climb, maybe best to start with 50-21, as it is slightly lower than 34-14, and also has the advantage that larger chainrings and sprockets wear slower than smaller ones. The only down side is that it will be a bit spinny on the flat. If you find it a bit of a slog on the hills, don't be put off straightaway. The extra strength builds quite quickly in a few weeks.

 

[jazzkat]

Lots of sensible comments already so I've not much to add.
I've been riding about 68 inches over winter and it's a bit too spinny on the flat but it's a lot easier on the up hill bits. In summer when I don't need lights and 'guards and my bike is lighter, I'm on about 75 inches. Much quicker overall, just a little bit tougher on the hills.

Another way to think about this, is work out your comfortable cruising speed at a comfortable cadence then work backwards from that.
So for example, if you usually ride with a cadence of around 85rpm and you feel you could easily hold 18mph on a flat then try something like 50x18 (73 inch).

I use this calculator:
http://www.bikecalc.com/
it seems a lot easier to play around with the numbers.
Good luck, don't forget to report back

 

[Tin Pot]

39/15 would be a good guess? (And you will probably find that a real grind on the hills!) That is the gear that I chose for my s/s bike and the gear was ok from 12-24 mph and ideal for me at about 18 mph. (On the flat!)

Managed to (replace inner tube without breaking never levers, woot!) get out for half an hour this evening on 34/15.

It was depressingly boring on the way out, flat and downhills, but a bit more demanding than usual on the way back.

Positives
I can immediately see why you attack the hills more.
Overall for an easy route I definitely worked harder.

Negatives
To be peddling all the time I had to have the brakes on a lot
I would have died on a fixie when an oncoming white hot hatch "appeared from nowhere".

Inconclusive. I'll try a week like this to see where it leads.

 

[fossyant]

Don't you need to factor in the greater drivetrain losses of a derailleur? So pick 5-10% fewer gear inches than the single speed you're considering?

Drive train loss. God how crap is your rear mech ? The difference is not noticeable

 

[mjr]

Drive train loss. God how crap is your rear mech ? The difference is not noticeable

I push a gear 8% higher than I do trying to simulate it on a derailleur bike. Rear mech is whatever was bottom-but-one from Shimano five years ago, but there's also the small matter of a thinner chain running at a slight angle.

 

[mjr]

http://forum.ctc.org.uk/viewtopic.php?f=5&t=83381 links to some estimates.

 

[fossyant]

I don't notice any difference. And that's running with rear mechs over 20 years old but on ceramic bushes.

 

[Tin Pot]

Went out yesterday on 34/14, my usual 20k training run up Biggin hill and back.

On the positive side I'm working harder on the up hills and netting 2kph faster

I know I'm only two rides in but I really cannot imagine doing this on a fixie. I'm hitting 60kph on the down hills, I can't imagine my little legs keeping up with that.

is there some sort of technique I'm missing to get the legs moving round fast enough on downhills?

I start bouncing around on the seat and wobbling the bike...

 

[jim55]

I do this as well , I physically can't spin fast enough

 

[mjr]

Might get better answers if the thread title says fixie rather than single speed, @Tin Pot

 

[jazzkat]

It's a bit hard to describe but for me the bouncing means I'm letting the pedals push my legs and that there's too much of my weight going through the saddle.
I suspect it's actually harder to control on a single rather than a fixed.

 

[Old Plodder]

Seeing as you are riding in my old area, I was using a 63" fixed, others were on 68". Around Biggin/Cudham/Downe, & the North Downs/Weald areas regularly.
As you use a fixed more, your hips get more supple, so you 'bounce' less going down hill. Don't even think of not having 2 brakes, the hills are too steep.

 

[totallyfixed]

Went out yesterday on 34/14, my usual 20k training run up Biggin hill and back.

On the positive side I'm working harder on the up hills and netting 2kph faster

I know I'm only two rides in but I really cannot imagine doing this on a fixie. I'm hitting 60kph on the down hills, I can't imagine my little legs keeping up with that.

is there some sort of technique I'm missing to get the legs moving round fast enough on downhills?

I start bouncing around on the seat and wobbling the bike...

It takes a while [a few thousand miles ] before your pedalling technique becomes smooth enough to handle very high cadences. My record in km is 71, not something I would care to repeat any time soon! I see so many cyclists "pedalling squares", really awful waste of energy, riding fixed soon cures that!

 

[swee'pea99]

I'm not sure all the 50/16 type tips, however well meant, are really all that helpful. I'd go for a ride - one which you know will after 10-15 minutes give you a straight, flat mile or two with no interruptions. Ride on it for a while, shifting up & down a bit till you find your ideal gear for cruising comfortably at a reasonable speed. Then stop changing - stick with that gear for a week or two and see how you go. And yes, expect to find hills very hard going, but don't wimp out.

 

[jonny jeez]

before I buy a SS/fixie I was thinking of simulating it on my roadie simply by staying in a set gear throughout my usual training run.

How can I tell what you usually get on a SS/fixie and how that would translate on a multi speed?

My main concern is hills - I drop to absolute lowest gear and slowly grind up hills.

Cheers,

TP

If you are serious, then find the perfect gear ratio, disconnect the cable and use the stop limit screws ro fix the chain into that sprocket...you will truly experience. The dependency of a
single gear choice and get a much better idea.

Keep in mi d your from rings will still offer a choice for an emergency uphill.